The chromatic equivalence class of graph $\overline{B_{n-6,1,2}}$

By h(G,x) and P(G,λ) we denote the adjoint polynomial and the chromatic polynomial of graph G, respectively. A new invariant of graph G, which is the fourth character R₄(G), is given in this paper. Using the properties of the adjoint polynomials, the adjoint equivalence class of graph $B_{n-6,1,2}$ is determined, which can be regarded as the continuance of the paper written by Wang et al. [J. Wang, R. Liu, C. Ye and Q. Huang, A complete solution to the chromatic equivalence class of graph $\overline{B_{n-7,1,3}}$, Discrete Math. (2007), doi: 10.1016/j.disc.2007.07.030]. According to the relations between h(G,x) and P(G,λ), we also simultaneously determine the chromatic equivalence class of $\overline{B_{n-6,1,2}}$ that is the complement of $B_{n-6,1,2}$.